Master Operators Govern Multifractality in Percolation

Using renormalization group methods we study multifractality in percolation at the instance of noisy random resistor networks. We introduce the concept of master operators. The multifractal moments of the current distribution (which are proportional to the noise cumulants $C_R^{(l)}(x,x^{\mathrm{\prime }})$ of the resistance between two sites x and $x^{\mathrm{\prime }}$ located on the same cluster) are related to such master operators. The scaling behavior of the multifractal moments is governed exclusively by the master operators, even though a myriad of servant operators is involved in the renormalization procedure. We calculate the family of multifractal exponents ${\psi }_l$ for the scaling behavior of the noise cumulants, $C_R^{(l)}(x,x^{\mathrm{\prime }})\sim \mathrm{\mid }x-x^{\mathrm{\prime }}{\mathrm{\mid }}^{{\psi }_l\mathrm{/}\nu }$, where $\nu$ is the correlation length exponent for percolation, to two-loop order.